I've read about someone installing the knock sensor into one of the alternator bracket mounting holes and it's possible that the B18A block has a cast-in blank for the knock sensor that's just not drilled/tapped. If you've found an electronic way around it, it's not even really an issue then. Good luck with your project.
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Andy - Reinstated
Hybrid Forum Moderator
'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.